Advanced backlights for LCD cockpit displays Jaap Groeneweg (NLR) Stefan Carton (NDF) 21 st April, 2016
Introduction NLR NLR = Netherlands Aerospace Centre NLR contributes key technological and scientific expertise to aerospace activities in the Netherlands and abroad Netherlands Aerospace Centre, NLR Amsterdam, The Netherlands Tel: +31 (0)88 5113582 Website: www.nlr.org E-mail: groenewg@nlr.nl Advanced backlights for LCD cockpit displays, 21 st April 2016 2
Introduction NDF Avionics Air Traffic Control Simulator Medical NDF Special Light Products BV Roosendaal, The Netherlands Tel: +31 (165) 538630 Website: www.ndf.eu E-mail: sales@ndf.eu Advanced backlights for LCD cockpit displays, 21 st April 2016 3
Trends in cockpit displays Increasing amounts and/or size of LCD displays: To present new types of information To integrate information on a single display Challenges on: Screen resolution Colour gamut Colour stability over lifetime Energy consumption Costs Thales avionics 2020 cockpit Advanced backlights for LCD cockpit displays, 21 st April 2016 4
Backlight performance Impact backlight on: Initial white point Colour stability over lifetime Energy consumption Costs (complexity) Colour gamut Advanced Remote Phosphor Technology (ARPHOS ) Advanced backlights for LCD cockpit displays, 21 st April 2016 5
ARPHOS technology Advantages remote phosphor: Lower phosphor temperature limited light depreciation and high color stability over lifetime Customized white point Color consistency: No LED binning issues for the customer Color filter ARPHOS Blue LED Advanced backlights for LCD cockpit displays, 21 st April 2016 6
NLR/NDF technology roadmap Based on proven stable materials. Next generation: replacement of remote phosphor by QD-sheets (currently not mature enough). Advanced backlights for LCD cockpit displays, 21 st April 2016 7
Next generation Quantum Dots What are Quantum Dots? QDs are small (nanometre scale) semiconductor nanoparticles Particle size determines absorption and emission wavelength QDs are highly suitable in backlighting because of the tuneable emission wavelength and the narrow-band emission Theoretical QD emission spectrum Advanced backlights for LCD cockpit displays, 21 st April 2016 8
Quantum Dots - opportunities Improved color gamut (for a typical avionics LCD with high NTSC colour filter) Remark: the colour gamut that can be realized also depends on the LCD colour filter characteristics 71% NTSC (CIE1931 xy) with traditional broad band emission phosphors 94% NTSC (CIE1931 xy) with narrow band emission quantum dots Quantum Dots and SAR (NVIS) By tuning the emission peak wavelength and peak width, it is possible to meet SAR (NVIS) requirements together with a reasonable colour gamut in Day modus. Advanced backlights for LCD cockpit displays, 21 st April 2016 9
DERPHOSA Development of a 15,4 Avionics Backlight based on remote phosphor Low power consumption of 20 Watt for 685 cd/m 2 (IPS LCD) Good uniformity with limited backlight depth (only 21 mm for a directlit) Weight < 2 kg Reduced complexity (compared to RGB-solution) Stable light output and colour point over lifetime (compared to white LEDs) Superior overall fault tolerance, by application of single color LEDs and driver/chain/block redundancy No color gamut improvement because of use of traditional phosphor materials (broad band emission) Advanced backlights for LCD cockpit displays, 21 st April 2016 10
DERPHOSA some pictures Derphosa BLU off Derphosa BLU on Derphosa BLU back Derphosa demonstrator on Farnborough Air Show Advanced backlights for LCD cockpit displays, 21 st April 2016 11
ARPHOS test results Customized white point Color point shift ARPHOS vs W-LEDs x = 0,254 ± 0,003 y = 0,219 ± 0,004 Production data backlight white point Same LED type Same circumstances Big difference Advanced backlights for LCD cockpit displays, 21 st April 2016 12
ARPHOS test results Stress test - 500 hours at 85 C / 85% r.h. Decrease in light output only 1 % Color point shift Δ u v = 0,0010 Advanced backlights for LCD cockpit displays, 21 st April 2016 13
ARPHOS test results HALT test DERPHOSA Decrease in light output only 2 % Color point shift Δ u v = 0,0016 Advanced backlights for LCD cockpit displays, 21 st April 2016 14
Conclusions ARPHOS ARPHOS technology based on traditional phosphors fulfils the requirements for the avionics market, except for colour gamut and SAR (NVIS). Quantum Dots The optimal solution to improve colour gamut is expected to be found in the quantum dot technique. By tuning the emission peak wavelength and peak width, it is possible to meet SAR (NVIS) requirements together with a reasonable colour gamut in Day modus. A disadvantage of quantum dots is the need for moisture barriers resulting in a more complex and expensive production process. Advanced backlights for LCD cockpit displays, 21 st April 2016 15
Derphosa display evaluation in NLR s laboratory aircraft GOAL: To perform an initial test of the display in a real aircraft under high brightness conditions that are not-achievable under laboratory conditions Direct sunlight, above clouds with cloud reflection High altitude: less water vapour, more UV light Demonstration in an operational environment (TRL 6) To get a qualitative measurement of the performance of the display Display comparison Using simulation and test patterns Using test subjects Advanced backlights for LCD cockpit displays, 21 st April 2016 16
Experiment set-up What to test? Readability: by comparing the new display with an existing display (3 variants) Distinguishability: by using a set of test patterns with different colours and fonts (4 variants) How to test? Using several test subjects (3 experts: commercial pilot, EASA, HMI) Using different sunlight directions (8 with 45 degree difference) With and without sunglasses (2) Using different positions (2: right seat, behind pedestal) Using questionnaires with rating scales Advanced backlights for LCD cockpit displays, 21 st April 2016 17
Readability test Simulation of similar symbology with and without SVS Existing display Title of presentation, date 2015 18
Distinguishability test Coloured squares, ghosting, coloured fonts test Advanced backlights for LCD cockpit displays, 21 st April 2016 19
Readability rating scale BASIC-T test Parameter = readability of all 5 indications: speed, attitude, altitude, heading, vertical speed Haworth-Newman rating scale based on Cooper- Harper rating scale Number of results measured: 3 x 3 x 8 x 2 x 2 = 288 Is satisfactory without improvement? NO YES Deficiencies warrant improvement Parameter characteristics Excellent, highly desirable Good, Negligible deficiencies Fair, some mildly Unpleasant deficiencies Minor but annoying deficiencies Moderately objectionable deficiencies Vert objectionable but tolerable deficiencies Demands on pilot in selected Task of required operation Pilot compensation not a factor for desired performance Pilot compensation not a factor for desired performance Minimal pilot compensation required for desired performance Desired performance requires moderate pilot compensation Adequate performance requires moderate pilot compensation Adequate performance requires extensive pilot compensation Pilot Rating 10 9 8 7 6 5 YES Is adequate performance attainable with a tolerable pilot workload? NO Deficiencies require improvement Major deficiencies Major deficiencies Major deficiencies Adequate performance not attainable with maximum tolerable pilot workload. Readability not in question Considerable pilot compensation is required to interpret symbology Intense pilot compensationis required to interpret symbology 4 3 2 YES Is parameter readable? NO Improvement mandatory Major deficiencies Symbology cannot be used for required operation 1 Pilot decisions Advanced backlights for LCD cockpit displays, 21 st April 2016 20
Distinguishability rating scale Simple rating scale Number of results measured: 4 x 3 x 8 x 2 x 2 = 384 Indicate for each colour the darkest square that still can be distinguished: Advanced backlights for LCD cockpit displays, 21 st April 2016 21
Results flown flight track Octagonal shape with 8 fixed headings to have 8 different sunlight directions Corrected heading for sun s changing azimuth angle each time when starting new round 6 rounds flown (3 test subjects X 2 tests) Advanced backlights for LCD cockpit displays, 21 st April 2016 22
Readability test results Overall rating for Derphosa display is more than 8, which means that display can be used without modifications Derphosa display is better than existing display No difference between standard PFD or SVS 0 = sun from behind, 90 = from the right, 180 = ahead, 270 = from the left Advanced backlights for LCD cockpit displays, 21 st April 2016 23
Distinguishability test results Strong influence of the black background Minimum intensity should at least 30%, for blue and red 50% Colour gamut may influence the results 0 = sun from behind, 90 = from the right, 180 = ahead, 270 = from the left Advanced backlights for LCD cockpit displays, 21 st April 2016 24
Distinguishability test results Strong influence by the black background Minimum intensity should at least 40%, for blue, red and magenta 80% Blue should not be used Colour gamut may influence the results Sunglasses and position influence ratings 0 = sun from behind, 90 = from the right, 180 = ahead, 270 = from the left Advanced backlights for LCD cockpit displays, 21 st April 2016 25
Distinguishability test results Results are identical for both positions and with and without sunglasses Response of the display is about 10 milliseconds (based on display update and displacement of the squares) Smooth rolling or pitching to a maximum of ~14 degrees/second 0 = sun from behind, 90 = from the right, 180 = ahead, 270 = from the left Advanced backlights for LCD cockpit displays, 21 st April 2016 26
Conclusions display evaluation New display is performing good under all test conditions New display could be used without any modifications to the LCD and the backlighting TRL 6 is achieved. The display is demonstrated working in an operational environment Although quality of the new display is very high, attention should be given to the display content, especially coloured fonts (literature can give solutions and SAE standards can be found) Advanced backlights for LCD cockpit displays, 21 st April 2016 27